Whining sound in 1992 Cadillac Seville and changing automatic transmission fluid

My Cadillac has started high pitched whining upon acceleration, increasing in pitch with higher rpm. This occurs even with a/c off and in park as well. My car is getting excellent gas mileage, and the
computer does not indicate anything is wrong. Is this serious?
How do I add fluids to the automatic transmission fluid? Could low fluid level cause this problem?
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Check the alternator.

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and the power steering pump...

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